Mopalia hindsii (Sowerby in Reeve, 1847)

Common name(s): Hind's chiton

Synonyms:  (Listed as Mopalia hindsi in some references) Mopalia hindsii
Phylum Mollusca
Order Neoloricata
Suborder Lepidopleurina
Family Mopaliidae
Mopalia hindsii feeding on the sponge Myxilla incrustans which is growing on the shell of the scallop Chlamys hastata.
(Photo by: Dave Cowles, July 2007)
Description:   This chiton has a girdle with sparse but easily seen dorsal, slender, flexible hairs which are not as long as the girdle is wide.  The branches of the hairs, if present, come only from the proximal parts of the larger hairs (photo).  There are no large granules on the dorsal surface of the girdle.  There is a pronounced cleft in the posterior end of the girdle (see photo above).  The ventral surface of the girdle is not orange (photo).  Plates 2-7 have rows of tubercles.  The lateral regions of plates 2-7 are separated from the central area by a slight, nearly smooth ridge or a series of slightly enlarged tubercles but not by a large ridge or a series of enlarged, coalesced tubercles.  May have very light blue lines on plates and the interior of the plates are white.  Length up to 10 cm.

How to Distinguish from Similar Species: Mopalia muscosa has dense, straplike hairs on the girdle. Mopalia lignosa has more hairs on the girdle and has no obvious rows of raised tubercles on the plates (but it does have pits), plus the posterior cleft in the girdle is absent or very small and the ventral girdle is orange.  Neither M. muscosa nor M. lignosa has a prominent posterior cleft in the girdle. Mopalia ciliata does have a prominent posterior girdle cleft but its girdle hairs are strap-shaped, have glassy spicules, and branch other than at the base.

Geographical Range:  SE Alaska to Ventura, CA.  This species is said to be very common in California but is not often mentioned in guides to the Pacific Northwest.

Depth Range:  Intertidal (and subtidal?)

Habitat:  Common intertidally under rocks, both on outer coast and in bays.

Biology/Natural History:  This species feeds on filamentous algae, diatoms, polychaetes, amphipods, and barnacles (and apparently on sponges).  It is common on shaded pilings, where the valves are often overgrown by bryozoans, annelids, barnacles, and hydroids.  The reproductive cycle is variable but in California it is mainly from October to March.  It  does not brood its young.  It may have the flatwormNexilis epichitonius symbiotic in its mantle cavity.



 

References:

Dichotomous Keys:
  Kozloff 1987, 1996
  Smith and Carlton, 1975
 

General References:
   Harbo, 1997
   Kozloff, 1993
  Morris et al., 1980
  O'Clair and O'Clair, 1998
  Ricketts et al., 1985

Scientific Articles:

Web sites:


General Notes and Observations:  Locations, abundances, unusual behaviors:
 

Grazing on sponge on scallop

This larger view shows how the chiton is grazing the sponge off the scallop.

Plates
This closeup shows the detail on the plates, plus a view of some of the girdle.


anterior plates
The anterior two plates of this individual have a lot of white.


Girdle hairs
This closeup of some of the sparse girdle hairs, along the lateral margin of the girdle, shows how the larger hairs branch from the base.  The orange/pink background is the sponge and scallop that the chiton is crawling on.  Other than on these lateral areas and in some areas along the edges of the plates the girdle hairs are quite sparse.

Girdle hair closeup
This closeup is of some girdle hairs which are not right at the margin of the girdle.

Underside
The underside of the girdle of this species is not orange.



Authors and Editors of Page:
Dave Cowles (2008):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)